|Results from the retort experiments for oil shale (OS) samples. Click to enlarge. Credit: ACS|
Researchers in Canada and Turkey have developed a new process that could lead to the more economical production of oil shale with increased yield. In laboratory-scale experiments, the researchers added inexpensive iron powder to four different types of oil shale combined with heating with electric coils. Production increased by more than 100% for one of the shale samples. Their study is scheduled for the November 19 issue of the journal Energy & Fuels.
Oil shale is a generic term applied to fine-grained sedimentary rock that contains significant amounts of kerogen, an organic precursor to oil and gas. Heated to the right temperature in the Earth’s crust, some types of kerogen release oil or gas. If such kerogens are present in high concentration in rocks, such as shale, and have not been heated to a sufficient temperature to release their hydrocarbons, they may form oil shale deposits.
The basics of releasing oil from oil shale is to heat the rock, either after mining in a retort, or in-situ via the use of electric heaters. (Earlier post.)
The easiest way to increase the efficiency of this method is to increase the thermal conductivity of the system or increase the reduction of the oil viscosity by using some additives. Metallic additives cause changes in the nature and the amount of fuel formed during in situ combustion.—Hascakir et al. (2008)
|Results from the in-situ heating simulations for oil shale (OS) samples. Click to enlarge. Data: Hascakir et al. (2008)|
The researchers used oil shale samples obtained from different oil shale deposits in Turkey and added three different iron powders at three different doses were used. The experimental results were simulated using a commercial reservoir simulator, where the data required for field-scale simulation were obtained through history matching of production data and temperature distribution inside the core. They also simulated field-scale application of in-situ electrical heating .
Because iron powders help increase the thermal conductivity of the system, heat transfer was accomplished more efficiently, yielding increased oil production at laboratory conditions. Also, iron additives have a catalytic effect that increases the reaction speed. The chemical reactions between iron powders and shale oil help to break the chemical bonds by increasing the temperature and magnetic effect of iron powders on the reduction of oil viscosity, which caused an increase in the oil production after the addition of iron powders.—Hascakir et al. (2008)
Introducing iron powder into the field for practical application with in-situ heating would be a critical enabler for this process. The researchers suggest that iron powders could be injected into the reservoir after mixing them with petroleum-based fluids, such as light oils or solvents. For fields shallow enough to support surface mining, a better solution would be adding the iron powders during the extraction process, they said.
The technical and economic feasibility analyses showed that electrical heating is still a marginal application, but the results proved that it is in an applicable range.—Hascakir et al. (2008)
A recent UC Berkeley analysis concluded that Shell’s in situ conversion process for oil shale produces an energy output of 1.2-1.6 times greater than the total primary energy inputs to the process. However, in the absence of capturing CO2 generated from electricity produced to fuel the process, well-to-pump GHG emissions are in the range of 30.6-37.1 grams of carbon equivalent per megajoule of refined fuel delivered (gCequiv/MJ RFD). These full-fuel-cycle emissions are 21%-47% larger than those from conventionally produced petroleum-based fuels. (Earlier post.)
Berna Hascakir, Tayfun Babadagli, and Serhat Akin (2008) Experimental and Numerical Simulation of Oil Recovery from Oil Shales by Electrical Heating. ASAP Energy Fuels, doi: 10.1021/ef800389v